We determined the prevalence of and the risk factors for human papillomavirus (HPV) infection and abnormal cytologic test results in 312 adolescent girls (mean age, 16.1 years). Subjects had a median of 2 years of sexual activity and 4 lifetime sex partners. Cervical HPV was detected by use of L1-consensus polymerase chain reaction in 64% of subjects; half of those with HPV had >1 type, and 77% had >/=1 high-risk type. Independent risk factors for HPV were lifetime number of sex partners, age of partner, and douching. Cytologic abnormalities were common (20.9% of subjects had atypical squamous cells of uncertain significance, and 17.0% had high- or low-grade squamous intraepithelial lesions) and were significantly associated with detection of HPV (P=.0001); however, most (51.6%) subjects with HPV had normal cytologic test results.
Genetic recombination involves classical crossing-over and gene conversion (aberrant segregation). In fungi that produce an ascus containing four spores, a gene conversion event is manifested as 3:1 or 1:3 (or more rarely 4:0 or 0:4) segregations, in contrast to the normal mendelian 2:2 segregation. Polarity is one of the properties of gene conversion; in almost all cases the frequency of conversion exhibits a gradient across the gene monitored. The frequency of conversion is usually independent of the specific allele used as a marker, but dependent on its location. An interpretation of conversion polarity is that it is caused by the existence of specific initiation sites for meiotic recombination, located at the high end of the polarity gradient. Here we show that the polarity gradient for the HIS2 gene of Saccharomyces cerevisiae is high at the 3' end of the gene, implying that the promoter of HIS2 is not the initiation site.
Background: The ninR region of phage λ contains two recombination genes, orf (ninB) and rap (ninG), that were previously shown to have roles when the RecF and RecBCD recombination pathways of E. coli, respectively, operate on phage λ.
Results: When λ DNA replication is blocked, recombination is focused at the termini of the virion chromosome. Deletion of the ninR region of λ decreases the sharpness of the focusing without diminishing the overall rate of recombination. The phenotype is accounted for in large part by the deletion of rap and of orf. Mutation of the recJ gene of the host partially suppresses the Rap– phenotype.
Conclusion: ninR functions Orf and Rap participate in Red recombination, the primary pathway operating when wild‐type λ grows lytically in rec+ cells. The ability of recJ mutation to suppress the Rap– phenotype indicates that RecJ exonuclease can participate in Red‐mediated recombination, at least in the absence of Rap function. A model is presented for Red‐mediated RecA‐dependent recombination that includes these newly identified participants.
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